Which device can convert all electrical energy into heat
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Water boils in an electric kettle in $15\,\min$ after switching on. If the length of the heating wire is decreased to $2/3$ of its initial value, then the same amount of water will boil with the same supply voltage in ............. $min$
It is preferable to measure the $e.m.f.$ of a cell by potentiometer than by a voltmeter because of the following possible reasons.
$(i)$ In case of potentiometer, no current flows through the cell.
$(ii)$ The length of the potentiometer allows greater precision.
$(iii)$ Measurement by the potentiometer is quicker.
$(iv)$ The sensitivity of the galvanometer, when using a potentiometer is not relevant.
Which of these reasons are correct?
In the meter bridge shown, the resistance $X$ has a negative temperature coefficient of resistance. Neglecting the variation in other resistors, when current is passed for some time, in the cirucit, balance point should shift towards.
A copper rod of cross-sectional area $A$ carries a uniform current $I$ through it. At temperature $T$, if the volume charge density of the rod is $\rho $, how long will the charges take to travel a distance $d$ ?
Two metal wires of identical dimensions are connected in series. If $\sigma _1$ and $\sigma _2$ are the conductivities of the metal wires respectively, the effective conductivity of the combination is
Four ammeters with identical internal resistance $r$ and a resistor $R$ are connected to a current source as given. if reading of $A_1$ and $A_2$ is $3\ A$ and $5\ A$ respectively then the reading $A_4$ is ............. $A$